1. Field of the Invention
This invention relates to vibration devices.
2. Description of the Prior Art
Vibration devices are used in applications such as pagers or mobile telephones (for “silent” call alerts and the like) and in computer game hand-held controllers (to give tactile feedback to the game player).
One type of previously proposed vibration device comprises a conventional rotary motor driving an eccentric mass or cam or the like, having its centre of mass displaced away from the axis of rotation. As the motor drives the offset mass around, a vibration is transmitted to the casing or other member to which the motor is attached.
Another previously proposed vibration device comprises a solenoid with a moveable mass (e.g. connected to a metal core within the solenoid) influenced by the magnetic field of the solenoid. The solenoid is fed with an appropriately alternating supply current so that the moveable mass is caused to oscillate and thereby to generate a vibration.
There is a constant need for vibration devices to be smaller and lighter, particularly in respect of mobile telephone applications.